The most recent one I've experienced is ElasticSearch + Kibana + FileBeat/MetricBeat. I've gone from munging through log files in a text editor or maybe LogParser to being able to quickly visualize issues in charts and dashboards, but then zoom into log-level details in seconds. It may not be fair to call notepad the "second best option", but for open source log (and more) analysis, Elastic+Kibana definitely stands out among competition.